Drive units for aircraft flaps connected to the leading and/or trailing edges of an aircraft wing convert a rotational movement into a translatory motion, whereby all drive shafts are coupled to a central drive.
Landing flaps hinged to the trailing edge of a wing and flaps for changing the aircraft wing cross-sectional configuration, such as leading edge flaps hinged to the leading edge of the wing, are conventionally operated by devices comprising a central drive unit operating two rotational shaft drives or drive trains for a left and a right aircraft wing. Such drive units further comprise a plurality of decentralized individual drive units with corresponding operating mechanisms. The central drive unit produces a rotational motion which is transmitted through the shaft drive train to the individual drive units allocated to the individual flaps. These individual drive units convert the initial rotational motion into a translatory motion which is transmitted to the respective operating mechanism which in turn operates the respective flaps as desired. In order to assure a uniform and synchronous operation of all flaps, it is conventional to connect all flaps of a wing with a common rotational shaft drive train. In ths context the term “flap” includes leading edge flaps and/or trailing edge flaps, whereby the latter may also be referred to as landing flaps.
It is, however, desirable to achieve an adjustment or positioning of individual flaps independently of the adjustment of any other flaps. Such independent or individual flap adjustments have aerodynamic advantages depending on any particular flight phase. These advantages include, for example the possibility of influencing a lift distribution over the wing span width, controlling air vortex formations caused by the wings, and an ability to compensate for asymmetric aircraft configurations. Such an asymmetric aircraft configuration may, for example, occur when an aircraft engines fails. The individual flap control permits counteracting the mentioned asymmetric situations by generating an oppositely effective lift asymmetry to thereby restore the desired symmetry of the aircraft control.
For reasons inherent in the flight mechanics it is generally necessary to provide for a symmetric position adjustment at the left and right aircraft wing. More specifically, flaps must be operated in pairs to achieve symmetric control configurations. Thus, the adjusted positions of the individual flaps at the left and right wing must be symmetric for pairs of flaps. However, under special flight conditions or for special applications it may be suitable and even necessary to establish non-symmetric or asymmetric flap position configurations.
Conventional control mechanisms of this type leave room for improvement with regard to the independent adjustment of individual flaps since conventionally such adjustments are generally not possible. However, devices are known which rely on a redundancy or multiplication of certain elements for a mechanical decoupling of different components of these devices to achieve a flap displacement individually and independently of any displacements of other flaps. However, such devices require the duplication of the number of drive units and of the rotational shaft drive trains. This duplication of components has a decoupling effect so that inner and outer pairs of flaps may be individually operated. Such redundant drive mechanism is known for example from the aircraft type Boeing B747. These known mechanisms make it possible to operate pairs of flaps symmetrically and independently of an operation of other flap pairs. More specifically, these known drives permit the symmetric adjustment of pairs of flaps as well as an asymmetric independent adjustment.
Moreover, it is known to have decentralized flap drive units which are mechanically decoupled from one another for operating individual flaps including landing flaps and/or leading edge flaps.
The redundancy of drive components required for the above conventional flap drives is a considerable disadvantage since the multitude of drive units including rotational shaft drive trains increases the weight of the aircraft due to the installation of a second central drive unit with its drive train and diverse additional gears and drive shafts which also require additional space and makes installation difficult. Moreover, drive mechanisms with decentralized individual drives that are mechanically decoupled from one another have the disadvantage that when dimensioning these drives the designer must take into account that any one of these individual drives may fail. This requirement normally leads to over-dimensioning these redundant drives which in turn results in heavier drive elements.